1. Field of the Invention
The invention relates to a temperature switch to be subjected to radiation heating from a radiation source and having at least one switch contact and a temperature sensor.
2. Prior Art
European Patent 116 861 discloses a temperature switch of the kind specified wherein a web made of the insulating material of the radiant heating element in which the switch is incorporated provides a radiation screen and therefore a temporary delay of response. This means that during starting phases of heating or boiling the radiant heating member can be brought to a higher temperature level, which during further operation is reduced to a permanent state which reliably prevents damage to the glass-ceramics plate during continuous operation.
Also as a result, the switching amplitude and hysteresis are increased, so that the switching frequency can be reduced to a permissible value in all conditions.
European Patent B 150 087 discloses a temperature switch for the heating of a glass-ceramics plate, wherein a quartz glass tube is used which selectively absorbs only radiation with a wave length which is radiated back from the glass-ceramics plate, to allow the temperature switch to respond to the temperature of the glass-ceramics plate. The radiation arriving from the radiation source is to be let through, but a temporary delay of response cannot be achieved.
For the same purpose and on the basis of the same principle, according to WO 85/01412 the expansion rod or the tube enclosing the rod is given a radiation-reflecting coating. The reflecting coating calls for additional steps in manufacture, and moreover its operation is endangered in operation, since the reflectivity may decline.